Speaker: Eric Zou

Title: Urban Forests: Environmental Health Values and Risks

Zoom Link: https://columbiauniversity.zoom.us/j/96154760758?pwd=WTduamNQcHFBaWhRS2NUNzdEc2xRZz09

Abstract: Forests accompany every city we build, but their impacts are poorly understood. We evaluate urban forests’ health values and risks through a massive afforestation program in the city of Beijing, which planted over a third of a million acres of greenery – roughly the size of Los Angeles – across the city over a decade. We conduct a remote-sensing audit of the program, finding that it contributes to a substantial greening up of the city. This causes significant downwind air quality improvement, reducing average PM2.5 concentration at city population hubs by 4.2 percent. Rapid vegetation growth, however, led to a 7.4 percent increase in pollen exposure. Analysis of medical claims data shows that increased aeroallergens triggered emergency room visits, mirroring pollution effects though much less severe. Monetized net health benefits of the program amount to 1.5 percent of the city’s GDP, on par with the cost of the program. We find an overall housing price appreciation near the afforested areas, although this effect does not align closely with urban forests’ downwind pollution impact gradient, and is thus more likely driven by the capitalization of localized amenities, such as aesthetic changes.